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<p>A library of astronomical calculations, providing positions, rise
and set times, magnitudes, and other information for the Sun, Moon
and planets.  The code is based on "Astronomical
Algorithms", by Jean Meeus, ISBN-10: 0-943396-61-1.  Implemented
directly in Java by Ian Cameron Smith.</p>

<p>The key class is {@link org.hermit.astro.Observation}.  It's used like this:

<ul>
<li>An application first creates an {@link org.hermit.astro.Observation} object using
    one of its constructors.</li>
<li>The application uses the set methods of {@link org.hermit.astro.Observation} to
    configure the position and date/time of the desired data, and any
    other factors as desired.</li>
<li>The application calls
    {@link org.hermit.astro.Observation#getBody(Body.Name which)} to
    get each of the astronomical bodies for which data is required.  The
    methods {@link org.hermit.astro.Observation#getSun()},
    {@link org.hermit.astro.Observation#getMoon()} and
    {@link org.hermit.astro.Observation#getPlanet(Body.Name which)} are
    convenience methods which return a {@link org.hermit.astro.Sun},
    {@link org.hermit.astro.Moon} or {@link org.hermit.astro.Planet}
    object; these are subclasses of {@link org.hermit.astro.Body}.</li>
<li>Finally, the application calls
    {@link org.hermit.astro.Observation#get(OField key)} to
    get computed global data about the observation, such as the current value
    for nutation; and/or {@link org.hermit.astro.Body#get(Field key)} to get
    computed data on a specific body, such as it's azimuth or magnitude.</li>
</ul>

<p>The {@link org.hermit.astro.Observation} and
{@link org.hermit.astro.Body} computes the requested data on
demand.  However, the data is cached, so that if it is referred to from
multiple places (which is often true in the internal calculations), it is
only calculated once.  Changing the circumstances of the observation
(position, time, etc.) automatically clears all cached data.</p>

<p>See <a href="http://code.google.com/p/moonblink/wiki/OnWatch">the
On Watch application</a> for an example of how it can be used.</p>

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